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991.
A quantum pseudo-spin model with random spin sizes is introduced to study the effects of charging-energy disorder on the superconducting transition in granular superconducting materials. Charging-energy effects result from the small electrical capacitance of the grains when the Coulomb charging energy is comparable to the Josephson-coupling energy. In the pseudo-spin model, randomness in the spin size is argued to arise from the inhomogeneous grain-size distribution. For a particular bimodal spin-size distribution, the model describes percolating granular superconductors. A mean-field theory is developed to obtain the phase diagram as a function of temperature, average charging energy and disorder. 相似文献
992.
Amrinder S. Nain Metin Sitti Annette Jacobson Tomasz Kowalewski Cristina Amon 《Macromolecular rapid communications》2009,30(16):1406-1412
Polymeric nanofibers are finding increasing number of applications and hold the potential to revolutionize diverse fields such as tissue engineering, smart textiles, sensors, and actuators. Aligning and producing high aspect ratio fiber arrays (length/diameter > 2 000) in the sub‐micron and nanoscale diameters has been challenging due to fragility of polymeric materials, thus making it difficult to deposit them as one dimensional structures functionally interfaced with other systems. Here, we present a pseudo dry spinning technique which allows precise control on fiber diameters and further allows deposition of fiber arrays in aligned configurations. Control on fiber diameters ranging from 50–500 nm and having lengths of several millimeters is achieved by altering the polymeric solution concentration. In the dilute and semi‐dilute unentangled concentration domain droplets or beaded fibers are observed to form. Smooth uniform diameter fibers are observed to form at the onset of semi‐dilute entangled concentration regime. For a given molecular weight, the increase in fiber diameter with increasing solution concentration is attributed to both the increase in the entanglement density and the decrease in the radius of gyration of solvated polymer molecules. Using this technique polymeric fiber arrays in single and multiple layers are demonstrated which can be used towards developing strong textiles, biological scaffolds, and sensor networks.
993.
分别在HF水溶液、含NH4F和H2O的乙二醇有机溶液中对Ti箔进行阳极氧化,得到TiO2纳米管阵列结构.该结构高度有序、分布均匀、垂直取向,且通过阳极氧化工艺条件(如阳极氧化电压、电解液的选择与配比以及氧化时间等)可实现对其结构参数(如管径、管壁厚度、管密度、管长等)的有效控制.利用XRD研究了TiO2纳米管阵列的物相结构.结果表明:退火前的TiO2纳米管阵列为无定形结构;分别在真空和氧气氛中50
关键词:
2纳米管阵列')" href="#">TiO2纳米管阵列
阳极氧化
可控生长 相似文献
994.
基于偏振阵列的偏振迈克耳孙风场探测干涉仪系统的理论研究 总被引:2,自引:0,他引:2
基于偏振阵列的偏振迈克耳孙风场探测干涉仪是一种新型的探测大气温度和风场速度的干涉仪.基于偏振干涉的原理,四个偏振方向分别相差45°的偏振片组成的偏振阵列紧贴于探测器前,由四面角锥棱镜出射的四束线偏振光分别经四个不同偏振方向的偏振片后,四个不同强度干涉图同时成像于探测器上,经过数据提取获得四个干涉强度值,进一步反演出大气温度和风场速度值.对以上干涉成像过程进行了模拟仿真,得到干涉图,经风速反演得到了与实际值一致的结果.具有结构简单稳定,测试精度高,利于快速变化的目标测试的优点. 相似文献
995.
996.
A method is presented for predicting the performance of multilayered piezoelectric structures which demonstrate two, loosely coupled compressional modes of vibration. A linear systems, lattice approach is developed using a matrix formulation for implementation of the transducer transfer functions in the frequency domain. The technique is computationally efficient, providing good results over a key range of transducer dimensions and is especially useful for the practical evaluation of multilayered, linear or diced array structures. 相似文献
997.
998.
The radius of curvature of the input surface of a thick lens spatial integrator array is a free parameter that can be customized for a maximum flux transfer efficiency. With this procedure each element is different but the spatial integration feature remains for the whole array. The calculation is based on a real ray-tracing evaluation that also takes into account the transmissivity of the diopters. The flux transfer on the synthetic image is doubled when the input surfaces are propoerly optimized. 相似文献
999.
Y.‐G. Guo C.‐J. Li L.‐J. Wan D.‐M. Chen C.‐R. Wang C.‐L. Bai Y.‐G. Wang 《Advanced functional materials》2003,13(8):626-630
Fullerene nanowire arrays with well‐defined size and length have been prepared by a controllable technique. Fullerene molecules such as C60 are introduced into the pores of anodic aluminum oxide (AAO) templates under a direct current (DC) electric field and polymerized in the pores. Structure analysis shows that the C60 nanowires are mainly polycrystalline, and a rhombohedral polymeric phase is observed in their vibration spectra. The electrical conductivity of so‐prepared nanowire arrays show a semiconducting behavior. The ability to fabricate the fullerene nanowire arrays with controlled structures represents an important step toward the development of chemical sensors and nanoscale electronic devices based on fullerenes. 相似文献
1000.
Lattice disregistry that exists in epitaxial overgrowths is often accommodated by interfacial dislocation arrays. The transition
between strain accommodation by uniform interfacial shear and by interfacial dislocations is fairly sharp and thought to be
controlled by energy minimization considerations. In this paper we demonstrate an extension of the Frank-van der Merwe approach
by incorporating the continuum methodology of Eshelby to the analysis of strain interactions between arrays of interfacial
dislocations in a bi-layered epitaxial film. Numerical examples are given for a Si/Si
x
Ge1-x
/Si heterostructure. The importance of such an analysis to the study of defect propagation through strained layer superlattices
is briefly discussed. 相似文献